Electron spectroscopy data for the high-temperature superconductors. What can we learn from it

An interpretation of spectroscopic data for the high temperature superconductors utilizing a highly correlated CuOn cluster model shows that a single set of Hubbard parameters predicts all of the state energies. Differences in the data from that for CuO are attributed to an increased Cu-O covalency in the superconductors. The reported temperature effects are attributed to increased metallic screening at lower temperatures.